Adrianne has taught high school and college biology and has a master's degree in cancer biology.

Learn all about passive immunity, including the different kinds and the various ways it is acquired and used. Then, check your new knowledge by taking a short quiz.

What is Passive Immunity?

Immunity refers to being protected or having a resistance to a particular illness or disease. You are immune to a disease or illness when your body creates antibodies to fight off the disease. Antibodies are blood proteins in your body that deactivate an infectious agent.

Passive immunity means that you gained resistance to the disease without having to actively do anything to gain resistance. In other words, you have received the antibodies that you needed to fight off an infection without your own immune system having to create the antibodies. This is in contrast to active immunity, in which your immune system has to be exposed to the disease in order to actually create the antibodies that are needed to fight the disease.

Wouldn't it be great if we could just get passive immunity to every disease without ever having to experience the disease itself? That would be nice, but there is a down side to it. Passive immunity is immediate, but it only lasts for a short time - a few weeks to 3 months - because your body doesn't know how to make the antibodies. So how do we get passive immunity?

What Is Natural Passive Immunity?

There are two main ways that passive immunity is acquired. One way is experienced by babies worldwide every day during fetal development. The baby acquires the antibodies in the mother's body, which she has created over her lifetime. This is called natural passive immunity. So see? We all experienced a little passive immunity at least once in life. Thanks, Mom!

There is another added benefit for babies that are breastfed. The first milk to come out is also packed with antibodies from the mother's body. This is a lot of the reason why pediatricians recommend breastfeeding, and why studies have shown that breastfed babies are healthier overall. The antibodies circulate for about 6 weeks and then they are no longer in the blood.

Unfortunately, you're past that point in life now, and that immunity is gone, so let's look at another way that passive immunity can be received.

What Is Artificial Passive Immunity?

You've probably heard of Ebola by this point. There have been numerous reports about how there were only a few doses of the antibody available to treat Ebola patients. Patients began coming to the U.S. to be treated, and there were more patients than there were doses of treatment. So what did the doctors employ in order to treat the remaining patients? They used artificial passive immunity, which occurs when the antibodies are taken from one person and given to someone else who needs them.

Here's how it worked: once the first two patients were treated, their blood contained the antibodies needed to fight off Ebola. The doctors removed some of the patients' serum, which is the part of the blood that contains antibodies. The antibodies from the serum were then administered to the rest of the patients, thereby giving them the antibodies necessary to fight off the disease. The patients that received the antibodies didn't have to make their own antibodies, so they received passive immunity from the patients whose bodies did create the antibodies.

Lesson Summary

Passive immunity occurs when a person receives the antibodies necessary to fight off a disease or infection. Passive immunity doesn't last very long, while active immunity lasts for the duration of your life. We were all given a one-time gift of natural passive immunity when our mother passed on her antibodies to us prior to birth. Breastfeeding also passes on antibodies, so it's another way to gain passive immunity. We can also gain artificial passive immunity when we receive antibodies from the serum of a person who has antibodies to a particular disease or infection.

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